Pollination has been in the news a lot recently: pollinators are dying out due to pesticides, diseases, and not being able to find enough food. This is a big problem for many crops and wild plants because many depend on pollinators in order to reproduce. Read on for the steamy details on pollination and how it supports the existence of our crops and wild plants.
Table of contents
What is pollination
Flowers have both male and female parts. The male part is made up of the anthers, which are supported by filaments. The anthers are important because they produce pollen. The female part is made up of a sticky stigma that is connected to an ovary with eggs inside. In order to make seeds, the pollen from the anthers needs to reach the stigma. However, there is a little problem. Plants need their pollen to reach another flower of the same species, but they cannot move. There are two solutions to this problem. The first is that wind can carry the pollen to another flower. The second is that pollinators carry pollen from one flower to another. This method is more efficient for flowers and therefore is used by most wild plants. Flowers want to attract pollinators so they produce sweet nectar at the base of their petals.
Pollinators do not know that plants want them to carry their pollen around. They are more concerned with getting food for themselves and their offspring. Nectar contains sugar and nutrients, which can give pollinators lots of energy, and pollen contains protein. Many pollinators have hairs, fur, or feathers. As they drink nectar or collect pollen, they rub against pollen from the anthers, which sticks on their fuzzy bodies. As they move on to the next flower, some of the pollen already on their bodies get stuck on the sticky stigma. The pollinators don’t even know that they are helping the plants out. Once pollen attaches to the stigma, it germinates. Pollen tubes form and stretch down until they reach the ovary. When they touch the egg, they fertilize it and form a seed. The seeds mature and when they are ready, they are released. These seeds grow up to be new plants.
Our tasty food depends on pollination!
5-8 % of global crop production is completely dependent on pollinators. However, this is not the whole picture, as many more crops are tastier, produce higher yields, or improved in some other way by pollination. Of the most used crops, 75% depend on pollination to some degree. For example, tomatoes that are pollinated by insects are bigger and taste better. If pollinators were to disappear, food production would be very strongly affected. Do you like chocolate? It depends on a single type of fly to pollinate it, if it were to go extinct, we’d be in trouble! Many other commodities that we enjoy also depend on pollination, such as coffee, almond milk, and exotic fruits.
Did you know that different fruits and vegetables depend on pollinators in different ways?
Curcurbits such as squash, zucchini, pumpkins, melons and watermelons need pollinators. They have separate male and female flowers and need pollinators to transfer pollen from the male flowers to the female flowers. If this does not occur, there aren’t any vegetables.
Soloanaceae such as tomatoes, bell peppers, eggplants, and chili peppers can have male and female parts in the same flower so they are able to self-pollinate but have a higher yield, taste better and are bigger when insect pollinated. They have a special type of anther that needs to be vibrated at a particular frequency to release pollen. Insects such as bumblebees and other types of solitary bees buzz at this frequency and can effectively pollinate these plants.
There are vegetables that are not the fruits of pollination and do not explicitly require pollinators for their production, but need them to produce seeds. For example, roots like potatoes, carrots and onions; flowers like broccoli, leaves like salad, and herbs like thyme, basil, oregano, rosemary are not formed from a plant ovary. However, they do produce flowers that need to be pollinated to produce seeds and therefore for new plants to grow.
Some crops like corn, wheat, rice, barley, rye, and oats rely on wind pollination and do not need any insect pollination at all. These are dietary staples so at least their production would be stable in the absence of pollinators. These plants produce billions of pollen grains and only a few of them will reach the female parts of other plants and produce seeds. Some nuts such as walnuts, pistachios, and hazelnuts are wind pollinated. As they don’t need to attract pollinators, they have very small, plain flowers.
Some plants are self-incompatible. This means that they need pollen from a different variety. For example, a Gala apple cannot be pollinated by the pollen from another Gala apple. It needs pollen from another cultivar to produce a fruit, though some apple varieties are able to still produce some fruit without pollinators. For this reason, orchards also have crabapples or different types of cultivars that produce a lot of pollen so the apple flowers receive the pollen they need to develop into a fruit. Other examples of crops dependent on pollination are pears and almonds.
There are also fruits and berries that are self-compatible and can produce fruit without pollinators. They do require pollinators to increase the yield and quality of the fruit. For example, a raspberry flower is made up of 100-125 female parts. Each little segment of a raspberry is actually a tiny fruit, so at least 80 of these little fruits need to form to have a normal raspberry. If there are fewer segments, the raspberry falls apart or isn’t so juicy. Pollinators help spread pollen to more stigmas to make sure you have a nice, juicy raspberry. Cherries, peaches, strawberries, and plums are all self-fertile.
Most wild plants need pollinators
Pollinators aren’t just important for making sure that we have enough food to eat, they are important for all of the flowers in our gardens, in meadows, and everywhere else in nature! 90% of wild plants are insect pollinated. Many plant species are completely dependent on pollinators, while others produce more, better quality seeds when they are pollinated. Therefore, wild plants depend on insects so that they can produce new seeds and that new flowers can grow. Not to mention that many insects and other animals depend on plants for food. Some insect larvae, like caterpillars, depend on a single type of plant while they are growing up. For example, monarch caterpillars need milkweed. If they can’t find milkweed, then they don’t survive to make their impressive migration.
We do not know how a loss of pollinators would actually affect the world’s plants. Researchers can only guess what the world would be like without pollinators by looking at places in the world where lots of pollinators have already gone extinct and by performing experiments.
Hawaii is a place where many pollinators have gone extinct so we can look at the effects. Many flowers were pollinated by birds found only on the archipelago. One-third of 52 bird species in Hawaii have gone extinct and many others are so rare that they are not able to pollinate so many flowers. Plants native to Hawaii have thin, curved flowers specially adapted for bird pollination. Due to the loss of their pollinators, 31 of these plant species have gone extinct in the last century. Many other large groups of pollinators have gone extinct, including 52 endemic bee species in the same genus and 26 moth species. The common house plant, Hawaii palm (Brighamia insignis), otherwise known as cabbage on a stick, is possibly extinct in the wild due to the extinction of its only pollinator, a hawkmoth. Although there are many other problems, such as habitat loss and introduction of invasive species and diseases, the loss of pollinators is a major contributing factor to about half of the 1200 native plant species in Hawaii being at risk of extinction. Some plants on Hawaii are now pollinated by invasive birds or mammals, but many are left without pollinators. Hawaii is an extreme case because it has many species found only there that have specialized relationships. In this case, the loss of pollinators can have a big effect.
Researchers in Europe have also conducted some experiments to see what a meadow would look like with fewer pollinators. They engineered covers that they placed over parts of meadows so that fewer pollinators would visit those plants. After a four year period, they found out that pollinators are responsible for keeping meadows full of different flower species and producing more new plants. The sections with fewer pollinators had fewer new flowers growing and the ones that did grow weren’t represented by very many different species.
All in all, we have pollinators to thank for a smorgasbord of colorful, tasty food, not to mention the flowers that ornament our balconies, parks, and wild habitats, giving us something nice to look at and giving many animals the food and space that they need.